Io Voyager / Galileo Image Mosaic Globe

Publisher

USGS Astrogeology Science Center

Abstract

A global monochrome mosaic of the best resolution images from both Galileo and Voyager 1 was created that includes 51 Voyager 1 images with spatial resolutions sometimes exceeding the 1 km/pixel scale of the final mosaic. Although the subjovian hemisphere of Io was poorly seen by Galileo, superbly detailed Voyager 1 images cover longitudes from 240°W to 40°W and the nearby southern latitudes. Image resolutions in the mosaic range from 1.0 to 10 km/pixel along the equator, with the poorest coverage centered on longitude 50° W. To present more information-rich views of Io, the global color derived from the Galileo color images was superimposed on the more detailed, higher resolution monochrome (Galileo/Voyager 1) mosaic. The procedure adopted was to calculate color ratio images from the Galileo data and apply them to the monochrome mosaic, requiring that the color ratios of the composite images match the color ratios of the Galileo data. The Galileo SSI camera's silicon CCD was sensitive to longer wavelengths than the vidicon cameras of Voyager, so distinctions between red and yellow hues can be more easily discerned. The global mosaic was reprojected so the entire surface of Io is portrayed in a manner suitable for the production of a globe. A specialized program was used to create the "flower petal" appearance of the images; the area of each petal from 0 to 75 degrees latitude is in the Transverse Mercator projection, and the area from 75 to 90 degrees latitude is in the Lambert Azimuthal Equal-Area projection. The projections for adjacent petals overlap by 2 degrees of longitude, so that some features are shown twice. Names shown on the globe are approved by the International Astronomical Union. The number, size, and placement of text were chosen for a 9-inch globe. A complete list of Io nomenclature can be found at the Gazetteer of Planetary Nomenclature. The northern hemisphere is shown on the left, and the southern hemisphere is shown on the right.

Contact and Distribution

Format

Global Mosaic, Globe

Access Scope

Native Data Set Environment

Mission Names

Galileo, Voyager

Online Package Link

https://astrogeology.usgs.gov/search/map/io_voyager_galileo_image_mosaic_globe

External File Size

4080037

Online File Link

http://astropedia.astrogeology.usgs.gov/download/Docs/Globes/Io_globe.pdf

Contact Address

2255 N. Gemini Drive

Contact City

Flagstaff

Contact State

AZ

Contact Postal Code

86001

Contact Email

astroweb@usgs.gov

Geospatial Information

Target

Io

System

Jupiter

Object Type

Grid Cell

Raster Row Count (lines)

2304

Raster Column Count (samples)

1440

Quad Name

Horizontal Coordinate System Units

Degrees